The present invention relates to manufacturing of semiconductor elements using low-temperature plasma, and more particularly to a microwave plasma processing apparatus of a cavity resonance system favorable for processings such as etching, CVD, ashing or the like.
Processing such as etching, CVD, sputtering or the like using microwave plasma become indispensable technology to fine pattern forming and film forming of semiconductor elements.
Plasma generation by microwaves is broadly classified into two systems. One is an ECR (Electron Cyclotron Resonance) system using a resonance phenomenon combining frequency of cyclotron motion where electrons are moved in rotational motion on a plane perpendicular to a magnetic field and frequency of microwaves, and the other is cavity resonance system where electric field intensity of microwaves is strengthened by a cavity resonator, and free electrons existing in the space are accelerated by the strong electric field whereby plasma is generated. The former system is disclosed in Japanese patent application Laid-Open No. 13480/1981 and No. 155535/1981, and further improvement thereof is disclosed in Japanese patent application laid-open No. 13575/1987. The latter system is disclosed in Japanese patent application Laid-Open No. 96841/1981, and further improvement thereof is disclosed in Japanese patent application Laid-Open No. 103088/1988. Problems to be Solved by the Invention
When the ECR system is used, since energy of microwave is transferred to electons by the resonance phenomenon, the electric field intensity of the microwave required for generation and maintaining of plasma may be weak. In the ECR system, however, since a magnetic field is required, a problem exists in that improvement of uniformity of the plasma is difficult.
The cavity resonance system is a system to solve this problem and is also disclosed in U.S. Pat. No. 4,776,918 wherein a cavity resonator is separated from a plasma production chamber by a ceramic or quartz plate and a slit plate is provided. However, also in this cavity resonance system sufficient consideration has not been given to ensuring that the plasma is processed uniformly and stably.